Previous metadata values should be unset when updating metadata

When updating metadata, the other bindings (tested with Python, not sure about the others) will unset the previous metadata fields.

E.g., with the Python bindings:

>>> c = stripe.Customer.retrieve("cus_...")
>>> c.metadata
<StripeObject at 0x10577b868> JSON: {
  "A": "is for Aardvark", 
  "B": "is for Baboon"
}
>>> c.metadata = {'C': 'is for Cactus', 'D': 'is for Dachsund'}
>>> c.save()
>>> c = stripe.Customer.retrieve("cus_...")
>>> c.metadata
<StripeObject at 0x10577b868> JSON: {
  "C": "is for Cactus", 
  "D": "is for Dachsund"
}

The bindings correctly reset the 'A' and 'B' keys in the update request:

{
    metadata:
    {
        A: "",
        B: "",
        C: "is for Cactus",
        D: "is for Dachsund"
    }
}

However, when doing the same operation with the Java bindings:

Customer customer = Customer.retrieve("cus_...");

System.out.println("Before update:");
System.out.println(customer.getMetadata());

Map<String, Object> customerParams = new HashMap<String, Object>();
Map<String, String> customerMetadata = new HashMap<String, String>();
customerMetadata.put("C", "is for Cactus");
customerMetadata.put("D", "is for Dachsund");
customerParams.put("metadata", customerMetadata);

customer.update(customerParams);

customer = Customer.retrieve("cus_...");

System.out.println("After update:");
System.out.println(customer.getMetadata());

The result is:

Before update:
{B=is for Baboon, A=is for Aardvark}
After update:
{B=is for Baboon, A=is for Aardvark, C=is for Cactus, D=is for Dachsund}

The update request only sent the new metadata keys, but didn’t reset the previously existing ones:

{
    metadata:
    {
        C: "is for Cactus",
        D: "is for Dachsund"
    }
}

[jimdanz]

This is intended behavior. stripe-java objects do not implement “save” methods that take the in-memory object and persist it to the API. Instead, stripe-java objects implement an explicit update method, the contract of which is that it sends its map of parameters directly over the wire.

To unset a metadata key in stripe-java, pass empty string as the value. For instance, customerMetadata.put("D", "");

[jimdanz]

Ah sorry didn’t realize that stripe-java overrides our handling of empty string. Thanks for catching!